The Rossoneri, who had not won at the intimidating San Paolo for almost 13 years and were booed with almost their every touch, moved above Inter Milan and two points behind leaders Lazio after goals from Robinho and Zlatan Ibrahimovic.
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Milan left back Luca Antonini had his head in his hands for different reasons after 10 minutes when he was involved in a sickening clash with Napoli's Christian Maggio and had to be carried off the field with a neck brace as a precaution.
The right-back made the most of his chance by performing a neat one-two with Ronaldinho's stand-in Robinho, who sidefooted the ball into the corner from just inside the area after 22 minutes.
Oddo's 73rd-minute cross was then headed in by an unmarked Ibrahimovic, who later limped off with a knock but still managed to get involved in an on-field brawl from the bench.
"It was a difficult match, we defended well and it's a very important three points for us," Robinho told Sky TV.
"I'm used to playing further forward but it's fine behind the frontmen too," added Robinho who netted his second league goal of the season after being slow to settle since his August move from Manchester City.
